Internal condition estimating system and estimating method

Abstract

A method of estimating, as the charging rate of an electricity storage system, the internal condition of the electricity storage system including plural batteries, and an internal condition estimating system utilizing that method are provided. A voltage measuring unit 3 measures voltages of all batteries 1 configuring an electricity storage system block 2 . A system cell voltage determining unit 5 determines a system cell voltage that will be a reference for an estimation of the SOC value of the electricity storage system block 2 based on the voltage value of the plural batteries 1 measured by the voltage measuring unit 3 . The system cell voltage determining unit 5 obtains the system cell voltage by giving a weighting to the voltage value in accordance with the pre-calculated SOC value of the electricity storage system block 2 . The system SOC estimating unit 6 estimates the SOC value of the electricity storage system block 2 based on the current flowing through the battery 1 and the system cell voltage.

The invention claimed is: 
     
       1. An internal condition estimating system that estimates a system state of charge (“SOC”) of an electricity storage system block comprising a plurality of batteries, the internal condition estimating system comprising:
 a voltage measuring unit measuring a voltage of the plurality of batteries; 
 a current measuring unit measuring a current flowing through the plurality of batteries; 
 a system cell voltage determining unit determining, based on a voltage value of the plurality of batteries measured by the voltage measuring unit, a system cell voltage; and 
 a system SOC estimating unit estimating, based on the current flowing through the battery and the system cell voltage, the SOC of the electricity storage system block, 
 wherein the batteries in the electricity storage system block are connected in a multiple parallel-series connection, in which a plurality of groups are connected in parallel, the groups each including the batteries connected in series, 
 the current measuring unit is installed at one location in the electricity storage system block, and calculates the current value flowing through the battery that configures the electricity storage system block based on the current value measured at the installation location, 
 the system cell voltage determining unit determining the system cell voltage by giving a weighting to the voltage value in accordance with a pre-calculated SOC of the electricity storage system block. 
 
     
     
       2. The internal condition estimating system according to  claim 1 , wherein the system cell voltage determining unit comprises:
 a voltage value memory storing voltage values per a time of the plurality of batteries measured by the voltage measuring unit; 
 a voltage value selector selecting a maximum voltage value and a minimum voltage value among the voltage values stored in the voltage value memory; and 
 a determination condition memory storing a weighting condition for the maximum voltage and the minimum voltage. 
 
     
     
       3. The internal condition estimating system according to  claim 2 , wherein the determination condition memory stores the weighting condition which increases the weighting to the minimum voltage when charging/discharging of the electricity storage system block is performed within a low SOC region, and which increases the weighting to the maximum voltage when the charging/discharging is performed within a high SOC region. 
     
     
       4. The internal condition estimating system according to  claim 2 , wherein the determination condition memory stores:
 a first threshold in the SOC of the electricity storage system block; and 
 the weighting condition which adopts the minimum voltage as the system cell voltage when the SOC of the electricity storage system block is less than the first threshold, and which adopts the maximum voltage as the system cell voltage when the SOC of the electricity storage system block is equal to or greater than the first threshold. 
 
     
     
       5. The internal condition estimating system according to  claim 2 , wherein the determination condition memory stores:
 first and second thresholds in the SOC of the electricity storage system block; and 
 the weighting condition which adopts the minimum voltage as the system cell voltage when the SOC of the electricity storage system block is less than the first threshold, adopts as the system cell voltage, an average voltage that is an average value of the voltage values of the plurality of batteries when the SOC of the electricity storage system block equal to or greater than the first threshold but less than the second threshold, and adopts the maximum voltage as the system cell voltage when the SOC of the electricity storage system block is equal to or greater than the second threshold. 
 
     
     
       6. The internal condition estimating system according to  claim 4 , wherein the first threshold is set in a region where a slope of a charge/discharge curve of the electricity storage system block is gradual. 
     
     
       7. The internal condition estimating system according to  claim 5 , wherein the first threshold and the second threshold are set in a region where a slope of a charge/discharge curve of the electricity storage system block is gradual. 
     
     
       8. The internal condition estimating system according to  claim 1 , further comprising:
 a temperature measuring unit measuring a temperature of the plurality of batteries; and 
 a system cell temperature determining unit determining a system cell temperature that is a reference for the estimation of the SOC of the electricity storage system block, 
 wherein the system SOC estimating unit estimates the SOC of the electricity storage system block based on the current flowing through the battery, the system cell voltage, and the system cell temperature. 
 
     
     
       9. The internal condition estimating system according to  claim 1 , wherein as the pre-calculated SOC of the electricity storage system block, the SOC of the electricity storage system block estimated by the system SOC estimating unit is adopted. 
     
     
       10. The internal condition estimating system according to  claim 1 , wherein as the pre-calculated SOC of the electricity storage system block, the SOC estimated based on a relationship between an open circuit voltage of the electricity storage system block and the SOC is adopted. 
     
     
       11. An internal condition estimating method of estimating a state of charge (“SOC”) of an electricity storage system block comprising a plurality of batteries, wherein the batteries in the electricity storage system block are connected in a multiple parallel-series connection, in which a plurality of groups are connected in parallel, the groups each including the batteries connected in series,
 the internal condition estimating method comprising:
 a voltage measuring step of measuring a voltage of the plurality of batteries; 
 a current measuring step that calculates a current value flowing through the storage batteries based on a current value measured at one place of the storage system section; 
 a step of selecting a maximum voltage value and a minimum voltage value among the voltage values that are measured in the voltage measuring step; 
 a system cell voltage determining step of determining a system cell voltage by giving a weighting to the maximum voltage value and the minimum voltage value in accordance with a pre-calculated system SOC; and 
 a system SOC estimating step of estimating, based on the current flowing through the battery and the system cell voltage, the SOC of the electricity storage system block. 
 
 
     
     
       12. The internal condition estimating method according to  claim 11 , further comprising a step of calculating a provisional system SOC,
 wherein in the system cell voltage determining step, the system cell voltage is determined by giving a weighting to the maximum voltage value and the minimum voltage value in accordance with the provisional system SOC. 
 
     
     
       13. The internal condition estimating method according to  claim 11 , wherein in the system cell voltage determining step, the system cell voltage is determined by giving a weighting to the maximum voltage value and the minimum voltage value in accordance with the pre-calculated system SOC that is the SOC estimated by system SOC estimating step.